1. Field of the Invention
The present invention relates to a ceiling fan and more particularly, to a method of controlling a speed of a brushless motor of a ceiling fan and the circuit thereof.
2. Description of the Related Art
In the market, a conventional ceiling fan usually takes a speed of a rotation of fans as a main control parameter. To control the fans by a constant-speed control system, the manufactures usually set different output PWM (Pulse Width Modulation) duties according to the loadings of the fan in the factory that the fans rotate in different speeds according to the set output PWM duties. In this way, the control program will provides variable settings according to the loadings of the fans that it has a problem for customization.
The fans of the ceiling fans usually have different sizes, different shapes, and different materials that will produce variable types of fans. However, the set output PWM duties are invariable that the ceiling may not work according to the original setting when the fans are replaced by different types of fans. For example, when the fans are replaced by heavier fans, the loading of motor will increase and only rotate the fans in a slower speed. However, the constant-speed control system will detect the speed is slower and call the motor providing more PWM duty. At the end of this condition, the motor may burn because of overheat and overload. In conclusion, it is not enough to control the speed of the ceiling by the constant-speed control system.